The invention relates to the fields of immunology and molecular medicine. In particular, it relates to diagnostic methods involving the determination the amount of intact genes of the FcγRII/FcγRIII gene cluster and to uses thereof in disease management, for example to predict whether a subject is predisposed for acquiring a disease or to predict the therapy responsiveness of an individual patient. It also relates to probes and nucleic acid constructs for use in such methods.
Sequencing the human genome has prompted many technical advances and stimulated the discoveries of various genomic landmarks. One area is the development of a dense set of polymorphic markers for gene mapping. The most common form of DNA sequence variation is a single nucleotide polymorphism (SNP) but, in addition, there are microsatellite repeat polymorphisms and insertion/deletion polymorphisms. Whereas SNPs and microsatellites have been very well characterized in terms of their genomic locations and their frequencies in different populations, insertion/deletion polymorphisms are less well characterized. Recent papers (see for example Sebat J. et al. Large-scale copy number polymorphism (CNP) in the human genome. Science 2004; 305: 525-528) described the identification of large (several kilobases to megabases) deletions and duplications of DNA fragments when genomes of normal individuals were compared. The identification and characterization of CNPs show that in addition to single-nucleotide differences, genomes of unrelated individuals have large regions of thousands to millions of nucleotides that are different.
From a functional perspective, gene copy number differences can contribute to variation in gene expression. CNPs of coding and regulatory regions are likely to affect expression of genes at the transcript and/or protein levels. Gene expression studies have shown that subtle differences in expression levels of genes have significant consequences. For example, copy number polymorphism of the defensin gene cluster probably accounts for natural variation in the expression level of DEFB4 which, in turn, might account for individual differences in immune defence (Linzmeier et al., Genomics. 2005; 86:423-30). Furthermore, Gonzalez et al. (Science. 2005; 307:1434-40) reported that possession of a CCL3L1 copy number lower than the population average is associated with markedly enhanced HIV/acquired immunodeficiency syndrome (AIDS) susceptibility. Cappuzzo et al. (J. Natl Cancer Inst. 2005; 97:643-55) disclosed that patients with advanced non-small-cell lung cancer whose tumour cells contain extra copies of the epidermal growth factor receptor (EGFR) gene may be more likely to respond to the drug gefitinib (Iressa), and suggested that this high gene copy number may be an effective predictor of gefitinib efficacy.
Thus, evidence is accumulating that CNPs and their overall effect on gene expression contributes significantly to the variation that underlies individual differences in predisposition to complex diseases.